Crystalline InAs and GaSb layers grown by molecular-beam epitaxy have been studied with high-resolution electron energy-loss spectroscopy (HREELS). From the observation of optical surface phonons, resonance frequencies w TOand oscillator strengths AE could be determined. The values found for InAs(wro — 219 cm-1and Ae = 2.9) are in agreement with optically derived data from the literature. As for GaSb, the resonance frequency and the oscillator strength determined by HREELS are at variance with published values. Preliminary results on InAs-GaSb superlattices are presented. © 1987, American Vacuum Society. All rights reserved.